1 /* SPDX-License-Identifier: GPL-2.0 */ 1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __VDSO_HELPERS_H 2 #ifndef __VDSO_HELPERS_H
3 #define __VDSO_HELPERS_H 3 #define __VDSO_HELPERS_H
4 4
5 #ifndef __ASSEMBLY__ 5 #ifndef __ASSEMBLY__
6 6
7 #include <asm/barrier.h> 7 #include <asm/barrier.h>
8 #include <vdso/datapage.h> 8 #include <vdso/datapage.h>
9 9
10 static __always_inline u32 vdso_read_begin(con 10 static __always_inline u32 vdso_read_begin(const struct vdso_data *vd)
11 { 11 {
12 u32 seq; 12 u32 seq;
13 13
14 while (unlikely((seq = READ_ONCE(vd->s 14 while (unlikely((seq = READ_ONCE(vd->seq)) & 1))
15 cpu_relax(); 15 cpu_relax();
16 16
17 smp_rmb(); 17 smp_rmb();
18 return seq; 18 return seq;
19 } 19 }
20 20
21 static __always_inline u32 vdso_read_retry(con 21 static __always_inline u32 vdso_read_retry(const struct vdso_data *vd,
22 u32 22 u32 start)
23 { 23 {
24 u32 seq; 24 u32 seq;
25 25
26 smp_rmb(); 26 smp_rmb();
27 seq = READ_ONCE(vd->seq); 27 seq = READ_ONCE(vd->seq);
28 return seq != start; 28 return seq != start;
29 } 29 }
30 30
31 static __always_inline void vdso_write_begin(s 31 static __always_inline void vdso_write_begin(struct vdso_data *vd)
32 { 32 {
33 /* 33 /*
34 * WRITE_ONCE() is required otherwise 34 * WRITE_ONCE() is required otherwise the compiler can validly tear
35 * updates to vd[x].seq and it is poss 35 * updates to vd[x].seq and it is possible that the value seen by the
36 * reader is inconsistent. 36 * reader is inconsistent.
37 */ 37 */
38 WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[ 38 WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[CS_HRES_COARSE].seq + 1);
39 WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW]. 39 WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW].seq + 1);
40 smp_wmb(); 40 smp_wmb();
41 } 41 }
42 42
43 static __always_inline void vdso_write_end(str 43 static __always_inline void vdso_write_end(struct vdso_data *vd)
44 { 44 {
45 smp_wmb(); 45 smp_wmb();
46 /* 46 /*
47 * WRITE_ONCE() is required otherwise 47 * WRITE_ONCE() is required otherwise the compiler can validly tear
48 * updates to vd[x].seq and it is poss 48 * updates to vd[x].seq and it is possible that the value seen by the
49 * reader is inconsistent. 49 * reader is inconsistent.
50 */ 50 */
51 WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[ 51 WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[CS_HRES_COARSE].seq + 1);
52 WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW]. 52 WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW].seq + 1);
53 } 53 }
54 54
55 #endif /* !__ASSEMBLY__ */ 55 #endif /* !__ASSEMBLY__ */
56 56
57 #endif /* __VDSO_HELPERS_H */ 57 #endif /* __VDSO_HELPERS_H */
58 58
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.